Could you please check if only SSL 2.0 protocol is enabled for Internet Explorer on your machine? If so, please see if enabling any of the other protocols would help. Note to refresh the page inside VS after applying the above mentioned changes.
Another possible solution will be to close any opened Visual Studio instances, delete the AppBuilder authentication cookie and try again. You can find it here: %localappdata%\Telerik\BlackDragon\IceCookie.bin
I hope the above helps. Please, let me know if you will require further assistance.